L merrill



March 31, 1964 G. L. MERRILL 3,126,623

PROCESS AND MEANS FOR HOT METAL FORMING Filed Aug. 21, 1951 INVENTOR. GERALD L. MERRILL ATTO RN EYS United States Patent 3,126,623 PROCESS AND MEANS FOR HOT METAL FORMING Gerald L. Merrill, Detroit, Mich., assignor to Smith- Morris Corporation, Ferndale, Mich., a corporation of Michigan Filed Aug. 21, 1961, Ser- No. 132,916 4 Claims. (Cl. 29-421) My invention relates to a novel hot-working process and means for metal forming by the application of explosive forces transmitted through a hot fluid medium.

Many hot-working techniques have bee-n commonly used, such as hot-forging, hot-rolling and hot-forming of metals. Many metals are not formable at ordinary room temperature, and the past practice of heating such metals before forming is well known to those skilled in the art.

Such hot-working techniques for the hot-forming of metals allow the working of metals at temperatures where they are most ductile and readily deformed into the desired form or shape. As the temperature of most metals rises, they lose their strength and become more ductile: hot-working of metals is thus an absolute necessity in the metals industry.

Recently a great deal of research has been carried on in the field of explosive metal working, which is found to have many particular advantages over other, more conventional methods of forming metals. The ability of the process to produce bulged configurations in split or separable dies is a certain mechanical advantage. Minimizing of spring back and increasing the extent to which metals can be deformed without rupturing are two advantages which are not entirely explainable, but are proven accomplishments.

The object of my invention is to improve upon the commonly used methods and means of today and to produce superior end results by combining the known techniques of hot working of metal with explosive-metal forming, and such a process as I have developed has an entirely new scope of possibilities, heretofore not thought practical or even envisioned. Molybdenum and its alloys, columbium, vanadium, and tungsten and its alloys are all important metals which require advanced or new methods of working before their full utility can be realized.

The application of explosive forces transmitted through a hot fluid medium can be advantageously used in many types of metal working, such as forming, bending, drawing, compacting, hardening and extruding of metals or non-metallic materials.

My present process includes the use of any chemical or electrical explosion or sudden release of energy including slow burning, deflagrating explosives, high detonating explosives, high voltage, electrical discharge or high velocity mechanical impact. The new process includes the use of any acceptable hot fluid medium maintained at a higher than ambient temperature by any suitable heating means, such as hot air, hot water, hot oil, molten salts and molten metals. As of now, I prefer to use most generally, molten salts.

In order to better understand the invention, reference may be had to the accompanying drawing illustrating one preferred piece of equipment found to be acceptable for use in carrying out my process, and in which FIG. 1 is a vertical cross-sectional view through a molten salt bath in an explosive forming tank, and

FIG. 2 is a cross section of the insulated explosive charge as used in carrying out the process.

The furnace or tank 10 preferably provided with a conventional ceramic lining 1.1 is closed by a splash cover 12, and is constructed of sufiicient size to accommodate the relatively large and heavy die 14. A metal forming blank 15 is inserted into the die cavity, which in this instance has a bulge or recess 16 into which the metal blank is to be pressed. Customarily the recess 16 is emptied of air by a vacuumline 13 leading to a suction motor (not shown) in the conventional manner. The tank is filled with the fluid medium 23, preferably salt, which is suitably heated to a molten state by an immersion heater 18 or other suitable means, and finally an explosive charge 17 is inserted into the interior of the die, inside the metal blank. A suitable cover 19 is employed to cover the die cavity and is arranged to have a seal tight fit therewith to seal the vacuum cavity or recess in the die.

Referring more particularly to FIG. 2 it will be evident that the explosive charge 21 is effectively insulated from the hot bath by the fact that the explosive charge 21 and detonator 22 are preferably cast in an asbestos-plaster mold 20, which will readily disintegrate upon detonation of the explosive. The tank is preferably constructed of a heat and shock resistant material.

Thus, by employing the explosive forming principle in which the forces are transmitted through a hot fluid medium, which preferably comprises in many applications, a molten salt bath, it has become possible to form end products of superior quality formed of materials which have heretofore been unsuitable for shaping by previously known methods.

The precise temperature and the composition of the hot fluid medium will more or less be varied depending on the character of the metal to be shaped or formed. On exploding the charge, the forces generated by said explosion, be it either a chemical, electrical or other sudden relcase of energy, form the metal blank in the die more advantageously and free of spring back when employing the hot fluid medium 23 for transmitting said forces.

ill; will be apparent to those skilled in the art to which my invention pertains, that while I have illustrated but one preferred form of my invention, that various changes and modifications may be made without departing from the spirit of my invention or from the scope of the appended claims.

I claim:

1. A method of forming metal comprising (a) providing a receptacle for retaining a fluid bath,

(b) heating said fluid bath to a temperature higher than ambient temperature,

(0) submerging a forming die, a metal forming blank and an explosive charge in said heated fluid bath, and

(d) detonating said explosive charge to form said metal blank in said die.

2. The process as defined in claim 1 and including the step of insulating said explosive charge from said heated fluid bath.

3. A metal forming means comprising (a) a receptacle and a fluid medium carried by said receptacle,

(b) means carried in said receptacle for heating said fluid medium and maintaining same at a higher than ambient temperature,

(0) a die and means retaining said die submerged in said fluid medium,

(d) a metal blank supported in said die,

(e) an explosive charge immersed in said fluid medium and supported in said receptacle in a position relative to said die to form said metal blank upon detonation of said explosive charge, and

(f) means for insulating said explosive charge from said fluid medium. I

4. The means as defined in claim 3 and in which said 3 insulating means comprises a frangible material readily 2,770,874 disintegrated upon detonation of said explosive charge. 2,935,038 References Cited in the file of this patent 2983242 UNITED STATES PATENTS 5 1,793,054 Carns Feb. 17, 1931 4 2,202,042 Blount May 28, 1940 1 4 Lindow Nov. 20, 1956 Chatten May 3, 1960 Cole May 9, 1961 FOREIGN PATENTS Germany July 4, 1877 Great Britain June 13, 1918 

1. A METHOD OF FORMING METAL COMPRISING (A) PROVIDING A RECEPTACLE FOR RETAINING A FLUID BATH, (B) HEATING SAID FLUID BATH TO A TEMPERATURE HIGHER THAN AMBIENT TEMPERATURE, (C) SUBMERGING A FORMING DIE, A METAL FORMING BLANK AND AN EXPLOSIVE CHARGE IN SAID HEATED FLUID BATH, AND (D) DETONATING SAID EXPLOSIVE CHARGE TO FORM SAID METAL BLANK IN SAID DIE. 